Ionization of multielectron atoms by strong static electric fields

We present two procedures for the calculation of ionization rates of multielectron atoms. The validity of the procedures is established by comparison with exact field ionization rates of helium. Better than 85% accuracy at field strengths of up to 1 a.u. is obtained with a frozen core model, when the exact field-free ground state is included. A Hartree-Fock calculation gives above-barrier ionization rates that are accurate to 75% or better.